The invention relates to a self-expansion electrical circuit breaker comprising:
a sealed enclosure filled with a high dielectric strength gas, PA1 an arc extinguishing chamber located inside said enclosure and having a communication orifice with the enclosure and a wall arranged as a piston, movement of which causes a variation of the volume of the extinguishing chamber, said piston being urged towards the minimum extinguishing chamber volume position and moving due to the action of a pressure increase in the extinguishing chamber to increase the volume of the latter, PA1 a pair of contacts disposed in the arc extinguishing chamber, said communication orifice being closed off in the closed position of said pair of contacts and opening when separation of the contacts occurs to allow the compressed arc puffing gas drawn between the contacts of the extinguishing chamber to be outlet to the enclosure.
An electrical circuit breaker of the kind mentioned, notably medium or high voltage, requires a relatively low operating energy and enables the current to be broken by deriving the puffing energy from the arc, from the heat rise due to the arc. The puffing effect is no longer obtained by a mechanical piston effect, but by a heat rise due to the action of the arc which depends on a number of factors, notably the current intensity flowing in the circuit breaker, the volume of the extinguishing chamber and the speed of separation of the contacts. It is difficult to design a self-expansion circuit breaker capable of interrupting both low intensity currents, and very high intensity short-circuit currents. A chamber of small volume is well-suited to breaking weak currents but when a short-circuit current occurs, the volume of puffing gas is insufficient. If an extinguishing chamber with a large volume suited to breaking strong currents is used, the pressure increase is insufficient to blow out weak current arcs.
The object of the invention is to achieve a self-expansion circuit breaker having an arc extinguishing chamber with a volume adjusting to the intensity of the arc to be extinguished.